steamhead: help with Megasteam Sizing...

jpf321

OK since I'm no longer concerned much with a gas conversion, I'm looking strongly at the Burnham Megasteam .. however, I need a bit of help with sizing ..



I currenlty have 384sq ft of EDR, mains are fully insulated with 1" and PVC jackets/inserts on the fittings.



I have 2 mains, each 2" which branch from boiler and join together at the far end to a wet return making a big loop .. 1 main is 65ft@2" the other is 55ft@2" .. therefore, I don't think I need to worry much about extra P/U factor.



I would like to use the boiler to make DHW .. whether it be by indirect or by tankless coil .. however, I've heard that a tankless coil could really collapse my steam in the boiler ..



I have an empty Electric HW heater/tank next to the boiler currently and would like to use that if I can as an indirect (although I'm not exactly sure how.. but that's for another discussion) ..



So the crux of my problem .. the Megasteam comes in either a 396sq ft or the next size up is 513sq ft .. the 513 seems quite a bit bigger than I need .. and the 396 seems just border line.



And then how best to make my DHW using the boiler... Tankless Coil or Indirect? and does a Tankless Coil significantly affect steam production?



thanks!

Patrick_North

First things first-

Assuming you've already tightened up your envelop, you may find that you can lower your attached EDR and still match heatloss. I spent almost two years juggling, removing, and replacing rads prior to our boiler replacement. Connected radiation is still ample (and even), though I lowered the EDR by over 200.

Also, much has been written here lately on effective, intentional undersizing of steam boilers. I believe this is mentioned in Dan's new book, too?

Good luck,

Patrick

jpf321

good point

Thanks Patrick -- good point .. i will probably tighten my envelope within the coming seasons .. so it may be the case that I will be able to reduce the connected load. Unless anyone yells and shouts, I will likely lean towards the 396 rated unit.  

Steamhead

Go with the 396

it has plenty of capacity for what you want to do. I'd use an indirect rather than a tankless, but your existing tank can be used for increased storage.

jpf321

thanks ..

thanks for the sizing help! i've been told that i can't use the empty tank for storage since it needs to have taps for recirc. i may look at the alliance SL for indirect regardless .. i'm not married to this empty tank.